See MetaData for details of what all these entries mean. Note that the set
of meta-data types (and the aliases used to refer to them) may be extended
by Foswiki extensions.

Most things at the top level of the plan - META:TOPICPARENT, META:TOPICINFO etc - are structures which are indexed by keys. For example, META:TOPICINFO has 4 entries, which are indexed by the keys author, date, format and version. META:FILEATTACHMENT, META:FIELD and META:PREFERENCE are all arrays, which means they can have any number of records under them. Arrays are indexed by numbers - for example, the first entry in the META:FIELD array is entry [0].

It's a bit clumsy having to type META:FILEATTACHMENT every time you want to refer to the array of attachments in a topic, so there are some predefined aliases that make it a bit less typing:

attachments means the same as META:FILEATTACHMENT

info means the same as META:TOPICINFO

createinfo means the same as META:CREATEINFO

parent means the same as META:TOPICPARENT. Note:parent is itself a map; use parent.name to access the name of the parent topic

moved means the same as META:TOPICMOVED

form means the same as META:FORM, so to test if a topic has a form named 'UserForm' you test for "form.name ~ '*.UserForm'"

fields means the same as META:FIELD, You can also use the name of the form (the value of form.name e.g. PersonForm)

preferences means the same as META:PREFERENCE

extensions may add additional aliases when they register new meta-data types

Fields in this plan are referenced using a simple field specifier syntax:

Note: at some point Foswiki may support multiple forms in the same topic. For this reason you can use the name of the form on the left-hand side of . and [] expressions. As long as there is only one form in the topic, it will have the same effect as the fields accessor.

If you use the name of a field (for example, LastName) in the query without a . before it, that is taken to mean "the value of the field named this". This works if and only if the field name isn't the same as of the top level entry names or their aliases described above. For example, the following expressions will all evaluate to the same thing:

Lastname

PersonForm.Lastname

Lastname.value

If the field name would conflict with the name of an entry or alias (e.g. it's moved or maybe parent), you can prepend the name of the form followed by a dot, as shown in the last example. You cannot refer to fields that have
the same name as operators (e.g. AND, not etc)

Note: some search implementations have difficulty with expressions that rely
on database values to disambiguate the syntax of the expression. If you don't
get the expected result from a query search, then make sure all references
are fully qualified.

Basic Types

The query language supports five basic types:

String - string constants are delimited by single quotes. Any values taked from topics (such as field values) are by default interpreted as strings. The empty string evaluates to boolean 'false', as does the string "0". All others evaluate to 'true'.

Number - numerical constants can be expressed using standard floating point number notation. Strings can also be used wherever a number is expected, in which case the string will be parsed as a number. Numerical 0 evaluates to boolean 'false', all others to 'true'.

Undefined - an undefined value is a placeholder for a value.

Array - ordered collections of values

Structure - also known as a "hash", a structure is an associative array that maps names to values. Topics are structures, with fields as described above.

Boolean values

Foswiki is implemented in Perl, and the query language inherits perl semantics for the query operators. This is usually only a problem when determining if a value is "true" or not.

Constants

You use constants for the values that you compare with fields. Constants are either strings, or numbers.

String Constants

String constants are always delimited by single-quotes. You can use backslash \ to include the following special characters:

LHS is less than RHS. If both sides are numbers, the order is numeric. Otherwise it is lexical (applies to all comparison operators)

5 < 4

>

greater than

4 > 5

<=

less than or equal to

2 <= 1

>=

greater than or equal to

2 >= 1

LC

Converts string to lower case, Use for caseless comparisons.

lc 'XYZ' will yield 'xyz'

UC

Converts string to UPPER CASE. Use for caseless comparisons.

uc 'xyz' will yield 'XYZ'

D2N

Converts a string representing a date (expressed in one of the formats that Foswiki can parse) to a number of seconds since 1st Jan 1970. This is the format dates are stored in inside Foswiki, and you have to convert a string date using D2N before you can compare it with - for example - the date an attachment was uploaded. Times without a timezone are assumed to be in server local time. If the text string is not recognised as a valid date, then D2N will return undefined.

d2n '25-Dec-2011'

NOT

Invert the result of the subquery

not(Size < 2)

AND

Combine two subqueries

(Length > Width) and (Age < Beauty)

OR

Combine two subqueries

(Length > Width) or (Age < Beauty)

INT

return the integer portion of a value (returns undef if the string isn't an integer, so beware.)

(1,2,3) expands to an array containing the scalar values [1,2,3], If either side of this operator returns an array value, that array will be flattened into the result i.e. ((1,2),(3,4)) is equivalent to (1,2,3,4)

+

Arithmetic addition, and string concatenation. String concatenation applies if either side of the expression does not evaluate to a number.

1 + 2

-

Arithmetic subtraction

2 - 1

-

Unary minus

-Size

*

Arithmetic multiplication

Buck * Doe

DIV

Arithmetic (real number) division

Rabbits div Stoats

IN

Test if a value is in a list

1 in (2, 3, 4)

Note that operator names are not case sensitive. AND is the same as and.

If you want to know if a field is undefined (has never been given a value) then you can compare it with undefined.

In the operators ( = != ~ =~ < > <= >= NOT AND OR) an undefined operand is treated the same as numerical 0. For lc uc d2n an undefined operand will give an undefined result. For length and undefined operand will give a result of 0.

Putting it all together

When a query is applied to a topic, the goal is to reduce to a TRUE or FALSE value that indicates whether the topic matches that query or not. If the query returns TRUE, then the topic is included in the search results.

A query matches if the query returns one or more values when it is applied to the topic. So if I have a very simple query, such as "attachments", then this will return TRUE for all topics that have one or more attachments. If I write "attachments[size>1024 AND name ~ '*.gif']" then it will return TRUE for all topics that have at least one attachment larger than 1024 bytes with a name ending in .gif.

Case sensitivity

The type=query search is always case sensitive, with the exceptions of:

operator names (and and AND are the same)

constants (now and NOW are the same)

Everything else is case sensitive. In order to do comparisons that are case insensitive, the recommended solution is to Use the lc() or uc() functions to convert either side of the comparison to be lower or upper case.
This is further demonstrated below in the examples.

Working with arrays

A number of fields in a topic are arrays, meaning that they refer to a list of values rather than a single value. Arrays are accessed using the square brackets ([]) and dot (.) operators.

The square brackets operator is actually a bit more clever than a simple query or array index. You can use the comma, operator inside the brackets to select a number of matching elements. For example,

versions[0,-1]

will select the most recent version (stored at index 0) and the oldest version.

You can even mix integer indices and conditions. For example, let's say we want to select all versions that are authored by 'RoaldDahl' and also select the oldest revision.

versions[-1,info.author='RoaldDahl']

Note that if 'RoaldDahl' authored the first revision, then you will get that revision twice in the result.

When the dot operator is applied to an array, it is applied to each element of the array, and the result is a new array containing the results of each application.

Working with versions

The versions field is mainly used with %QUERY to provide a powerful view into the history of a topic. It is an array of objects, one for each revision of the topic (including the most recent), where the most recent revision is in position [0] in the array, and the second most recent in [1] etc. You can use the versions field to select old versions based on a query. For example,

versions[info.author='RoaldDahl']

will return a list of all versions authored by RoaldDahl. You can access field
values in the topics as they were at the time - for example,

versions[info.author='RoaldDahl'].Published

will return an array of the values of the Published field in all versions authored by RoaldDahl.

When you access the topic history using the versions field, the history of the topic is loaded with the most recent revision first i.e. at index [0]. So versions[1] does not refer to version 1 of the topic; it refers to the version at position 1 in the array i.e. one before the most recent revision. If you want to access the version numbered '1', then you must use versions[info.version=1] (or versions[-1]).

WARNING: Some of the Foswiki store implementations use an external tool called RCS to store topic histories. RCS has very poor performance when it comes to recovering all versions. For this reason you should avoid use of queries that use versions if you are using one of these stores.

Gotchas

Remember that in the query language, topic names are constants. You cannot write Main.UserTopic/UserForm.firstName because Main.UserTopic will be interpreted as a form field name. If you want to refer to topics you must enclose the topic name in quotes i.e. 'Main.UserTopic'/UserForm.firstName

Query operations are performed in the context of =%WEB% and =%TOPIC%. This can cause confusing when they are used in an %INCLUDEed topic, where you might expect them to operate in the context of the including topic, rather than the included topic.

Examples

Query examples

attachments[name='purdey.gif'] - true if there is an attachment call purdey.gif on the topic

(fields[name='Firstname'].value='Emma' OR fields[name='Firstname'].value='John') AND fields[name='Lastname'].value='Peel' - true for 'Emma Peel' and 'John Peel' but not 'Robert Peel' or 'Emma Thompson'

(Firstname='Emma' OR Firstname='John') AND Lastname='Peel' - shortcut form of the previous query

HistoryForm[name='Age'].value>2 - true if the topic has a HistoryForm, and the form has a field called Age with a value > 2

HistoryForm.Age > 2 - shortcut for the previous query

preferences[name='FaveColour' AND value='Tangerine'] - true if the topic has the given preference settings and value

Person/(ClothesForm[name='Headgear'].value ~ '*Bowler*' AND attachments[name~'*hat.gif' AND date < d2n('2007-01-01')]) - true if the form attached to the topic has a field called Person that has a value that is the name of a topic, and that topic contains the form ClothesForm, with a field called Headgear, and the value of that field contains the string 'Bowler', and the topic also has at least one attachment that has a name matching *hat.gif and a date before 1st Jan 2007. (Phew!)

length(fields[NOT lc(attributes)=~'h']) - the number of fields that are not hidden

lc(name)=~'.*ann.*' - Would match Anne, Maryann, MaryAnn, AnnMarie...

Search examples

Find all topics that are children of this topic in the current web

%SEARCH{"parent.name = '%TOPIC%'" web="%WEB%" type="query"}%

Find all topics that have an attachment called 'grunge.gif'

%SEARCH{"attachments[name='grunge.gif']" type="query"}%

Find all topics that have form ColourForm where the form field 'Shades' is 'green' or 'yellow' but not 'brown'